The present invention relates to the field of electrical energy generation through solar power collection, and more particularly to solar power generation using free piston Stirling engines implemented in a directly illuminated solar cavity.
The desire to decrease and ultimately eliminate dependence on fossil fuels has stimulated research into clean and renewable ways to produce electricity for the global marketplace. Solar power has become a viable option because it is a clean form of energy production and there is a potentially limitless supply of solar radiation. To that end, it is estimated the solar energy flux from the sun is approximately 2.7 megawatt-hours per square meter per year in certain advantageous areas of the world. With this tremendous amount of free and clean energy available, and the desire to reduce dependence on fossil fuels, solar power production is now, more than ever, being reviewed as an important means to help meet the energy consumption demands in various parts of the world.
Technological innovations and improvements have helped to make terrestrial solar power generation a feasible means for large scale power production. More specifically, the reduction in the magnitude of capital investment required and the reduction in recurring operation and maintenance costs allow solar power generation to compete with other forms of terrestrial power generation. Further, the scalability of solar power plants has the potential to enable smaller facilities to be constructed, with production capacity on the order of ten kilowatts, for communities with smaller demands and larger facilities capable of producing one hundred megawatts or more for large metropolitan areas with higher energy demands.
To address the above demand for solar power systems many configurations have been designed and implemented. One such implementation is a concentrated solar power system that collects solar energy and concentrates that energy onto an absorber. The thermal energy from the absorber is then used to drive a conversion engine. Typical systems employ kinematic Stirling engines. Kinematic Stirling engines, however, utilize a crankshaft to extract power from the engine and turn an external generator to produce electricity. This requires a contacting lubricated seal on the crankshaft to seal and contain the high pressure working gas within the engine, resulting in a system with low reliability and high overall maintenance costs. The high recurring cost associated with the use of kinematic Stirling engines makes the present day solar power generation systems that require their use economically unattractive.
Accordingly, a need exists for a solar power generation system utilizing a reliable and cost effective mechanism for converting solar power into electricity.
The present invention provides a solar power system for converting sunlight (i.e., solar energy) into electrical energy. The solar power system utilizes at least one mirror to focus the sunlight into a cavity. The cavity is formed by a plurality of heat collectors, which function to absorb the incoming solar energy and conduct the energy to a plurality of free piston Stirling converters. The free piston Stirling converters convert the thermal energy into electrical energy. The solar power system of the present invention reduces the capital and recurring costs of typical solar power systems by using multiple free piston Stirling converters as the energy conversion device. In particular, free piston Stirling converters of a small size (less than 3 kW electric) are very simple by design and inexpensive to massproduce because the required heat exchangers can be incorporated within a simple monolithic heater head. Because surface area does not scale proportional to volume, larger scale free piston Stirling converters require heat exchangers, typically multiple tube heat exchangers, external to the core vessel, to provide the required heat transfer surface area resulting in a device that is complex and expensive to fabricate. Therefore, a system employing multiple Stirling converters of a smaller size that utilize a simple monolithic heater head type is more cost effective. Furthermore, the free piston Stirling converter consists of a Stirling engine and linear alternator all contained within a hermetic vessel. There is no crankshaft required to drive an external generator as with a kinematic Stirling engine. The free piston Stirling converter uses noncontacting clearance seals within the device, so there are no contacting parts to wear, resulting in very high reliability and low maintenance. Thus, the use of multiple free piston Stirling converters greatly reduces the overall capital cost and maintenance costs when compared to current systems employing large kinematic Stirling engines.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limited the scope of the invention.